A peristaltic pump functions like fingers holding a fluid filled tube. The fluid in the tube moves forward, as fingers slide forward. A peristaltic pump also adopts this principle by only replacing the fingers by a contact roller. The pump of fluid is achieved by alternately squeezing and releasing the flexible delivery tube of the pump. Like the fingers squeezing a flexible tube, with the movement of the fingers, a negative pressure is formed in the tube, therefore the fluid flows. A peristaltic pump is to form a “pillow” shaped fluid in the pump tube between two rolls. In industrial production, in many cases they need to add the liquid to the production apparatus by a peristaltic pump, so that the fluid may be remained in the flexible tube, or the speed of introducing fluid into the flexible tube is not fast enough. So that it is necessary to design an apparatus for squeezing the fluid in the flexible tube, on one hand, to increase the speed of introducing fluid into the flexible tube by alternately squeezing, on the other hand, to discharge the remaining fluid in the flexible tube by alternately squeezing, at the same time, the liquid delivery quantity can be accurate quantitative controlled.
Chinese patent CN 203161500 U discloses a linear peristaltic pump, comprising a frame, a lifting motion, an infusion set, an infusion flexible tube, a linear drive module, an on-off valve, and an extrusion roller assembly, wherein, the linear drive module is assembled on the frame, the infusion set is connected to the lifting motion, the on-off valve is fixed on the frame, the infusion flexible tube is assembled on the infusion set and passes through the on-off valve, the extrusion roller assembly is connected on the linear drive module. The invention increases the life time of the infusion flexible tube, occupied less space, and improves the accuracy of the delivery of fluid. But the accurate quantitative control of the liquid delivery quantity cannot be achieved by the invention, besides, the invention cannot prevent backflow very well.